Before getting behind the steering wheel, it’s important to be absolutely sure that you’re fit to drive. That means being safely below the government alcohol limit. Handheld breathalyzers are becoming increasingly popular personal devices – but do they actually work?

The answer isn’t straightforward: it essentially depends on the unit. Not all models on the market are created equal. Entry-level (read: inexpensive) devices are nice as gifts, but not as reliable test units. Professional-grade device that use superior technology, however, give you the accuracy you’re looking for. We’ve put together a checklist of what you should be looking out for.

Does the Device Use a Mouthpiece?

Mouthpieces are not the most practical attachments, however they do impact results for the better. They eliminate external air from entering the unit, which can sometimes distort results. Passive Testing Unites that only require you to blow into a hole will allow air pollutants to enter the unit, rendering the results unreliable at best.

Is the Unit DOT Cleared?

If your device does not have clearance from the Department of Transportation (DOT), you shouldn’t consider it as anything more than a novelty gift item. The reason for this is that DOT tests give you the guarantee that your unit performs according to strict specifications, giving you peace of mind.

Does the Unit Have Sensor Accuracy?

It’s important that the device has been tested for its sensor accuracy in a controlled environment. Check the packaging to see whether it has a sensor accuracy of +/- 0.01% at the very least. This ensures you get decent readings each and every time.

Can the Device Be Recalibrated?

It is highly likely that in order to maintain accuracy levels, you will need to periodically recalibrate your device. This process ensures that the software works in conjunction with the sensor, giving accurate results.

Cheaper units will often not have this option, meaning that results can be skewed over time. While this doesn’t matter too much if the device is simply being used as a party trick, it does mean that it should not be relied on for precise readings.

What About Compact iPhone Breathalyzers?

These smartphone devices have been getting quite a bit of press lately. Claiming to do everything a standard breathalyzer can do at a fraction of the size and price, a lot of people are opting for the recently released Breathometer.

While certainly an impressive device in terms of aesthetics and practicality, it simply does not live up the billing when it comes to accuracy. It claims to be ‘FDA Registered’, which actually doesn’t really say anything to back up whether it actually works. All this means is that it’s safe to use and won’t cause you harm. Contrary to popular assumption, it’s not proof for a product’s efficacy. When a company doesn’t make this clear, it’s not a good sign.

Keep in mind that breathalyzers come in all shapes and sizes. Ensure you go over the questions above when purchasing your unit. If you’re simply looking for a gift item to be used at social gatherings, accuracy can take a backseat. However, if you’re planning on basing important decisions on your unit’s results, such as whether to drive or not, make sure you purchase one that matches professional-grade standards.